Semiconductor device with air gap and method of fabricating the same

ABSTRACT

A method of fabricating a semiconductor device and a semiconductor device formed by the method. The method includes form a stack conductive structure by stacking a first conductive pattern and an insulation pattern over a substrate; forming a sacrificial pattern over sidewalls of the stack conductive structure; forming a second conductive pattern having a recessed surface lower than a top surface of the stack conductive structure; forming a sacrificial spacer to expose sidewalls of the insulation pattern by removing an upper portion of the sacrificial pattern; reducing a width of the exposed portion of the insulation patters; forming a capping spacer to cap the sidewalls of the insulation pattern having the reduced width over the sacrificial spacer; and forming an air gap between the first conductive pattern and the second conductive pattern by converting the sacrificial spacer to volatile byproducts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.14/015,423 filed on Aug. 30, 2013, which claims priority of KoreanPatent Application No. 10-2013-0041584, filed on Apr. 16, 2013.Thedisclosure of each of the foregoing application is incorporated hereinby reference in its entirety.

BACKGROUND

1. Field

Exemplary implementations of the present invention relate to asemiconductor device, and more particularly, to a semiconductor devicewith an air gap and a method of fabricating the same.

2. Description of the Related Art

In general, a semiconductor device may include, for example, conductivestructures formed with insulating a material provided therebetween. Withan increase in the of integration of semiconductor devices, a distancebetween the conductive structures has gradually decreased. Accordingly,parasitic capacitance between the conductive structures has increased.With the increase of parasitic capacitance, an operation speed of thesemiconductor device is degraded.

In order to reduce parasitic capacitance the dielectric constant of theinsulating a material is reduced. However, there is a limitation inreducing parasitic capacitance since the insulating a material have arelatively high dielectric constant.

SUMMARY

Various exemplary implementations are directed to a semiconductor devicethat may reduce parasitic capacitance between adjacent conductivestructures, and a method for fabricating the same.

An exemplary method of fabricating a semiconductor device includesforming a first conductive pattern over a substrate; forming aninsulation pattern over first conductive pattern to form a conductivestructure; forming a sacrificial pattern and a first insulating layer onthe conductive structure; forming, adjacent to the first conductivepattern, a second conductive pattern having a top surface that is lowerthan a top surface of the first conductive structure; removing an upperportion of the sacrificial pattern to form a sacrificial spacer exposinga portion of the insulation pattern and removing an upper portion of thefirst insulating layer to forma passivation spacer exposing a portion ofthe insulation pattern; reducing a width of the exposed portion of theinsulation pattern; capping the sacrificial spacer and the passivationspacer with a second spacer; and forming an air gap between the firstconductive pattern and the second conductive pattern by converting thesacrificial spacer to a diffusible state.

An exemplary method of fabricating a semiconductor device includesforming an insulation layer over a substrate; forming an open portion inthe insulation layer; forming a sacrificial spacer over sidewalis thatdefine the open portion; forming a passivation spacer over thesacrificial spacer; forming a recessed conductive pattern in the openportion; trimming an upper portion of the sidewalls that define the openportion; forming a capping spacer to cap the sacrificial spacer and thepassivation spacer; and forming an air gap between the recessedconductive pattern over and the sidewalls that define the open portionby converting the sacrificial spacer to a volatilized state.

An exemplary method for fabricating a semiconductor device includesforming, over a substrate, a plurality of bit line structures, eachincluding a stacked bit line and a hard mask pattern; forming aninter-layer insulation layer over the plurality of bit line structures;forming, by etching the inter-layer insulation layer, a contact holebetween the plurality of bit line structures; forming acarbon-containing spacer on sidewalls, of the plurality of bit linestructures, that define the contact hole; forming a first plug in thecontact hole to form a recess plug structure, including thecarbon-containing spacer, wherein the carbon-containing spacer islocated between the first plug and the sidewalls, of the plurality ofbit line structures, that define the contact hole; removing thecarbon-containing spacer to expose sidewalls of the hard mask pattern;reducing a thickness of the exposed the sidewalls of the hard maskpattern; forming a capping spacer to cap the carbon-containing spacerand the reduced thickness sidewalls of the hard mask pattern; and

forming an air gap between the bit line and the first plug by convertingthe carbon-containing spacer to a volatile form.

An exemplary semiconductor device includes a bit line structure formedover a substrate, the bit line structure including a bit line and a hardmask pattern, wherein the hard mask pattern has a width smaller than awidth of the bit line; a bit line spacer formed over sidewalls of thebit line; a first plug formed adjacent to the sidewalls of the bit lineand separated from the bit line by an air gap; and a capping spacerformed over the sidewalls of the hard mask pattern and the bit linespacer to cap the air gap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view illustrating an exemplary semiconductordevice.

FIGS. 2A to 2G are cross sectional views illustrating an method offabricating the exemplary semiconductor device of FIG. 1.

FIG. 3 is a modification of the exemplary semiconductor device shown inFIG. 1.

FIG. 4 is a cross sectional views illustrating an exemplarysemiconductor device.

FIGS. 5A to 5I are cross sectional views illustrating an method offabricating the exemplary semiconductor device of FIG. 4.

FIG. 6 is a modification of the exemplary semiconductor device shown inFIG. 4.

FIGS. 7A to 7D illustrate a comparative example with FIG. 4.

FIG. 8A illustrates exemplary memory cells of a semiconductor device.

FIG. 8B is a cross-sectional view of the exemplary memory cells takenalong line. A-A′ of FIG. 8A.

FIG. 8C is a cross-sectional view of the exemplary memory cells takenalong line B-B′ of FIG. 8B.

FIGS. 9A to 9K illustrate a method of fabricating the exemplary memorycells.

FIG. 10 is a schematic diagram of an exemplary memory card.

FIG. 11 is a block diagram illustrating an exemplary electronic system.

DETAILED DESCRIPTION

Various exemplary implementations of the present invention will bedescribed below in more detail with reference to the accompanyingdrawings. The present invention may, however, be embodied in differentforms and should not be construed as limited to the exemplaryimplementations set forth herein. Rather, these exemplaryimplementations are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the present inventionto those skilled in the art. Throughout the disclosure, referencenumerals correspond directly to the like numbered parts in the variousfigures and exemplary implementations of the present invention.

The drawings are not necessarily to scale and in some instances,proportions may have been exaggerated in order to clearly illustratefeatures of the implementations. It should be readily understood thatthe meaning of “on” and “over” in the present disclosure should beinterpreted in the broadest manner such that “on” means not only“directly on” but also “on” something with an intermediate feature(s) ora layer(s) therebetween, and that “over” means not only directly on topbut also on top of something with an intermediate feature(s) or alayer(s) therebetween.

FIG. 1 is a cross sectional view illustrating an exemplary semiconductordevice.

Referring to FIG. 1, an insulation layer 102 is formed over a substrate101. An open portion 103 is formed in the insulation layer 102. The openportion 103 may include, for example, a first open portion 103A and asecond open portion 103B. The first open portion 103A exposes a part ofa surface of the substrate 101. The second open portion 103B is formedover the first open portion 103A. A width of the second open portion103B may be greater than a width of the first open portion 103A. Aconductive structure 104 is formed in the open portion 103. Theconductive structure 104 may include a first conductive pattern 105 anda second conductive pattern 107. The second conductive pattern 107 isformed over the first conductive pattern 105. A third conductive pattern106 is formed between the first conductive pattern 105 and the secondconductive pattern 107. The third conductive pattern 106 is an ohmiccontact layer. The first conductive pattern 105 is formed in the firstopen portion 103A. The second conductive pattern 107 is formed in thesecond open portion 103B. An air gap 108 is formed between the firstconductive pattern 105 and sidewalls that define the first open portion103A. A first spacer 109 is formed over the sidewalls that define thefirst open portion 103A. The air gap 108 is formed between the firstspacer 109 and the first conductive pattern 105. A second spacer 110 isformed over the air gap 108 and the first spacer 109. The second spacer110 is formed over sidewalls that define the second open portion 103B tocap the air gap 108 and the first spacer 109.

The substrate 101 may include, for example, for example, a siliconsubstrate, a silicon germanium substrate, the like. Furthermore, thesubstrate 101 may include, for example, a silicon-on-insulator (SOI)substrate. The insulation layer 102 may include, for example, a materialhaving a low dielectric constant, such as silicon nitride, siliconoxide, or the like. The insulation layer 102 may include, for example,an inter-layer insulation layer.

The open portion 103 is formed to be a hole shape or a line shape. Forexample, the open portion 103 may be a contact hole, a via hole, athrough hole, a trench, a recess, or the like. The first open portion103A and the second open portion 103B may include, for example, thethrough hole. One of the first open portion 103A or the second openportion 103B may include, for example, the through hole, and the othermay have the line shape. If the open portion 103 is a contact hole, thenthe conductive structure 104 is a contact plug.

The first conductive pattern 105 may include, for example, asilicon-containing material, a metal-containing material, or the like.The second conductive pattern 107 may include, for example for example,a silicon-containing material, a metal-containing material, or the like.The first conductive pattern 105 and the second conductive pattern 107may include, for example, polysilicon, a metal, a metal nitride, a metalsilicide, a metal carbide, or the like. The first conductive pattern 105and the second conductive pattern 107 may include, for example the sameconductive material or may include, for example, different conductive amaterial from each other. For example, the first conductive pattern 105may include, for example, a silicon-containing material, and the secondconductive pattern 107 may include, for example a metal-containingmaterial. Alternatively, the first conductive pattern 105 may include,for example, a metal-containing material and the second conductivepattern 107 may include, for example, a silicon-containing material. Ifa silicon-containing first conductive pattern 105 contacts ametal-containing second conductive pattern 107, then an ohmic contactmay be required. The third conductive pattern 106 may act as the ohmiccontact layer. The third conductive pattern 106 may include, forexample, a metal silicide. The third conductive pattern 106 may include,for example, cobalt silicide, titanium silicide, or the like.

The first spacer 109 and the second spacer 110 may include, for example,a material having a low dielectric constant. The material having a lowdielectric constant may include, for example, an oxide or a nitride. Thematerial having a low dielectric constant may include, for example, asilicon oxide, a silicon nitride, or a metal oxide. The first spacer 109may include, for example, a material having a high density, and thesecond spacer 110 may include, for example, a material having a lowdensity. The first spacer 109 may include, for example, a siliconnitride, and the second spacer 110 may include, for example, a siliconoxide. The silicon oxide may include, for example, SiO₂. The siliconnitride may include, for example, Si₃N₄, SiN or the like. The secondspacer 110 may include, for example, a material having a low densitysilicon oxide. The low density silicon oxide is formed at a lowtemperature. A lower portion of the second spacer 110 is wide enough tocap the air gap 108.

The air gap 108 is formed by removing a sacrificial material through aconversion process. The sacrificial material is formed between the firstspacer 109 and the first conductive pattern 105. After capping thesacrificial material using the second spacer 110 the conversion processis performed. It will be descried more detail in FIGS. 2A to 2G.

Shown as FIG. 1, the air gap 108 is stably capped by the second spacer110. An electric insulating characteristic of the conductive structure104 is improved since the air gap 108 insulates the conductive structure104 from a certain conductive pattern which is disposed adjacent to theconductive structure 104. Also, if a certain conductive pattern isdisposed adjacent to the first conductive pattern 105, then a parasiticcapacitance between the certain conductive pattern and the firstconductive pattern 105 is decreased.

Since the second spacer 110 is formed over the sidewalls that define thesecond open portion 103B, a thickness of the second spacer 110 will bethick enough to cap the air gap 108, so that the air gap 108 is stablyprotected by the second spacer 110. In addition, by enlarging an area toform the third conductive pattern 106, a contact resistance between theconductive structure 104 and the first conductive pattern 105 may beimproved.

FIGS. 2A to 2G are cross sectional views illustrating an exemplarymethod of fabricating the semiconductor device of FIG. 1.

Referring to FIG. 2A, a first insulation layer 12 is formed over asubstrate 11. The substrate 11 may include, for example, a semiconductorsubstrate. The substrate 11 may contain silicon. The substrate 11 mayinclude, for example, a silicon substrate, a silicon germaniumsubstrate, or the like. Furthermore, the substrate 11 may include, forexample, a silicon-on-insulator (SOI) substrate. The first insulationlayer 12 may include, for example, a low-k material, such as siliconnitride, silicon oxide, or the like.

An open portion 13 is formed in the first insulation layer 12. The openportion 13 is formed to expose a surface of the substrate 11 by etchingthe first insulation layer 12. The open portion 13 is formed to be ahole shape or a line shape. For example, the open portion 13 may be acontact hole, a via hole, a through hole, a trench, a recess, or thelike. An open array may be formed by regularly arranging a plurality ofopen portions 13 at a certain interval. A mask pattern (not shown) maybe used to etch the first insulation layer 12. The mask pattern mayinclude, for example, a photoresist pattern, a hard mask pattern that ispatterned by a photoresist pattern, or the like.

A second insulation layer 14A is formed over the entire surface of theresulting structure comprising the first insulation layer 12 and theopen portion 13. The second insulation layer 14A may be conformallyformed to have a thin thickness. The second insulation layer 14A mayinclude, for example, a low-k material. The second insulation layer 14Amay include, for example, a low-k material having a high density. Thesecond insulation layer 14A may include, for example, silicon nitride.

A sacrificial layer 15A is formed over the second insulation layer 14A.The sacrificial layer 15A may be conformally formed to have a thinthickness. The sacrificial layer 15A may include, for example, a low-kmaterial. The sacrificial layer 15A may include a material, volatilebyproducts, diffused by a conversion process. The sacrificial layer 15Ais formed at a temperature above at least 400° C. The dielectricconstant of the sacrificial layer 15A has a value between a dielectricconstant of air and a dielectric constant of SiO₂(K_(air)<K_(sacrificial layer)<K_(SiO2)). The sacrificial layer 15A mayinclude, for example, a carbon-containing material. The sacrificiallayer 15A may include, for example, an amorphous carbon.

Referring to FIG. 28, a dual spacer structure is formed over sidewallsthat define the open portion 13. The double spacer structure mayinclude, for example, a first spacer 14B and a sacrificial spacer 15B.The sacrificial spacer 15B may be formed by etching the sacrificiallayer 15A, and the first spacer 14B may be formed by etching the secondinsulation layer 14A. An etch-back process may be used to etch the firstspacer 14B and the sacrificial spacer 15B. By forming the first spacer14B and the sacrificial spacer 15B, a surface of the substrate 11 isexposed through the open portion 13.

Referring to FIG. 2C, a first conductive pattern 16 is formed to fillthe open portion 13. A first conductive layer (not shown) is formed overthe first insulation layer 12 comprising the sacrificial spacer 15B. Thefirst conductive layer is formed to fill the open portion 13 over thefirst insulation layer 12. The first conductive layer is formed at a lowtemperature below at least 400° C. Then, the first conductive layer maybe selectively etched, thereby forming a first conductive pattern 16recessed in the open portion 13. The first conductive pattern 16 may beformed by etching the first conductive layer until the first conductivelayer is completely removed from a surface of the first insulation layer12. The first conductive pattern 16 may include, for example, asilicon-containing material or a metal-containing material. The firstconductive pattern 16 may include, for example, polysilicon, tungsten,titanium-nitride, a metal silicide, or the like. The first conductivepattern 16 is in contact with the surface of the substrate 11.

Referring to FIG. 2D, the sacrificial spacer 15B and the first spacer14B, exposed over an upper portion of the first conductive pattern 16,are recessed to a certain depth by an isotropic etching process.Accordingly, the sacrificial spacer and the first spacer are representedby reference numeral “15” and “14,” respectively.

By the isotropic etching process, a sacrificial spacer 15 is formed tosurround the first conductive pattern 16. Upper surfaces of thesacrificial spacer 15 and the first spacer 14 are aligned to an uppersurface of the first conductive pattern 16.

By the isotropic etching process, sidewalls that define an upper portionof the open portion 13 are exposed. The exposed sidewalls that define anupper portion of the open portion 13 are exposed sidewalls 13B. Aportion remained of a recessed structure is in a first open portion 13A.

Then, a trimming process may be performed on the exposed sidewalls 13B.The trimming process may be performed by an isotropic etching process. Aline width 13B of the first open portion 13 is increased by the trimmingprocess. A second open portion 13C is formed by trimming the exposedsidewalis 13B.

The open portion 13 has a dual structure comprising the first openportion 13A and the second open portion 13C. A width of the second openportion 13C is greater than a width of the first open portion 13A. Arecess structure is formed in the first open portion 13A. An upperportion of the recess structure is exposed by the second open portion13C. The recess structure may include, for example, the first conductivepattern 16, the sacrificial spacer 15 and the first spacer 14.

An etch-back process is applied to recess the first conductive pattern16A and the sacrificial spacer 15B.

Referring to FIG. 2E, a second spacer 17 is formed. The second spacer 17may be formed by etching a third insulation layer (not shown). The thirdinsulation layer is formed over the first insulation layer 12 and in thesecond open portion 13C. The third insulation layer may include, forexample, a material having a low dielectric constant of a low density.Generally, the low dielectric constant is below 3 and the highdielectric constant is above 7. The third insulation layer may include,for example, a porous dielectric material. The third insulation layermay include, for example, a silicon oxide, a silicon oxide having a lowdensity, or the like. Since the silicon oxide having a low density isvolatile byproducts, it is easily diffused by the conversion process.The silicon oxide having a low density may be formed by a lowtemperature CVD. Since the third insulation layer is formed at a lowtemperature below at least 400° C., the third insulation layer has a lowdensity. Since the third insulation layer may include, for example, amaterial having a low density, it is capable of being diffused by oxygenplasma in a plasma stripper. The third insulation layer may be etched toform the second spacer 17. The third insulation layer may be etched byetch-back process.

The second spacer 17 has a thickness sufficient to cap an upper portionof the sacrificial spacer 15. The second spacer 17 is formed to exposethe upper portion of the first conductive pattern 16. The second spacer17 is formed to cap the upper portions of the sacrificial spacer 15 andthe first spacer 14, and to expose the upper portion of the firstconductive pattern 16.

The first spacer 14 and the sacrificial spacer 15 are formed over thesidewalls that define the first open portion 13A. The second spacer 17is formed over the sidewalls that define the second open portion 13C.The second spacer 17 covers the upper portions of the first spacer 14and the sacrificial spacer 15. The sacrificial spacer 15 may not exposedsince the second spacer 17, the first spacer 14 and the first conductivepattern 16 surround the sacrificial spacer 15.

Referring to FIG. 2F, the sacrificial spacer 15 is removed, To removethe sacrificial spacer 15, a conversion process 18 is performed. Thesacrificial spacer 15 is turned into volatile byproducts 20 by theconversion process 18. The conversion process 18 may include, forexample, a decomposition process, a phase change process, or the like.The decomposition process and the phase change process turn a solid intovolatile byproducts 20, such as a vapor or a gas. The volatilebyproducts 20 are easily removed by diffusing through the second spacer17. Since a density of the second spacer 17 is low, the volatilebyproducts 20 are easily diffused through the second spacer.

If the sacrificial spacer 15 includes, for example, an amorphous carbon,then the conversion process 18 may include, for example, an oxidationreaction process, such as an O₂ plasma treatment process. The O₂ plasmatreatment process may be performed using a plasma stripper. Theamorphous carbon may be oxidized by the O₂ plasma treatment process, andthus, converted into a vapor or a gas. For example, when the O₂ plasmapermeates the amorphous carbon through the second spacer 17, theamorphous carbon is oxidized into the volatile byproducts 20, such ascarbon dioxide CO₂. The volatile byproducts 20 are diffused through thesecond spacer 17. The low density material of the second spacer 17allows the O₂ plasma to permeate through the second spacer 17, andallows the volatile byproducts 20 to diffuse out through the secondspacer 17. On the other hand, the first spacer 14 blocks the volatilebyproducts 20 from being diffused. Since the first spacer 14 mayinclude, for example, a high density material, diffusion of the volatilebyproducts 20 is blocked by the first spacer 14. That is, the firstspacer 14 acts as a passivation spacer for blocking the diffusion of thevolatile byproducts 20.

As the sacrificial spacer 15 is removed by the conversion process 18, aspace occupied by the sacrificial spacer 15 becomes an air gap 19. Sincethe air gap 19 is capped by the second spacer 17, the air gap 19 isstably capped even though the sacrificial spacer 15 is removed. Thesecond spacer 17 acts as a capping spacer. A parasitic capacitancebetween adjacent conductive structures is reduced by the air gap 19. Theair gap 19 is formed between the first conductive pattern 16 and thefirst spacer 14.

The air gap 19 is formed by removing the sacrificial spacer 15 throughthe conversion process 18. Thus, the sacrificial spacer 15 is removedwithout using an etching process, such as a wet etching process.

As described above, since the air gap 19 is formed without using anetching process, a loss to surrounding structures that would be causedby the etching process is prevented. Also, the sacrificial spacer 15 isremoved without a residue by the conversion process 18. Also, since theair gap 19 is formed after the second spacer 17 is formed, a cappingefficiency of the air gap 19 is increased. Also, the second spacer 17prevents an exposure of the air gap 19 and a flowing of a conductivematerial in to the air gap 19.

Referring to FIG. 2G, a second conductive pattern 22 is formed over afirst conductive pattern 16. The second conductive pattern 22 fills thesecond open portion 13C having the second spacer 17. The secondconductive pattern 22 may include, for example, a metal-containinglayer. The second conductive pattern 22 may include, for example, atungsten layer. The second conductive pattern 22 may include, forexample, a tungsten layer. The second conductive pattern 22 may include,for example, a stacked structure including a barrier layer and atungsten layer. The barrier layer may include, for example, a stackedstructure of a titanium layer and a titanium nitride layer.

A third conductive pattern 21 is formed over the first conductivepattern 16 and the second conductive pattern 22. The third conductivepattern 21 may form an ohmic contact between the first conductivepattern 16 and the second conductive pattern 22. The third conductivepattern 21 may include, for example, a metal silicide. The thirdconductive pattern 21 may include, for example, a cobalt silicide. Toform the cobalt silicide, an annealing process may be performed after acobalt layer is deposited over the first conductive pattern 16.Alternatively, a cobalt silicide may be directly deposited over thefirst conductive pattern 16. The deposited cobalt silicide may besimultaneously formed between the first conductive pattern 16 and thesecond conductive pattern 22 and between the second spacer 17 and thesecond conductive pattern 22.

A conductive structure 23, which includes the first conductive pattern16, the third conductive pattern 21 and the second conductive pattern22, is formed. The air gap 19 and the first spacer 14 are formed betweenthe first conductive pattern 16 and sidewalls that define the first openregion 13A. The second spacer 17 is formed between the second conductivepattern 22 and sidewalls that define the second open region 13C. Thesecond spacer 17 caps the air gap 19 and the first spacer 14

The conductive structure 23 may become a contact plug, an electrode, orthe like by subsequent processes. Further, conductive structure 23 maybecome a bit line, a metal interconnection, a gate electrode, a wordline, or the like by a subsequent process.

Since the second spacer 17 is formed over the sidewalls that define thesecond open portion 13C, a thickness of the second spacer 17 issufficient to cap the air gap 19, so that the air gap 19 is stablyprotected by the second spacer 17. In addition, by enlarging an area toform the third conductive pattern 21, a contact resistance between thefirst conductive pattern 16 and the second conductive pattern 22 may beimproved.

FIG. 3 shows a modification of the exemplary semiconductor device shownin FIG. 1.

Referring to FIG. 3, an insulation layer 102 is formed over a substrate101. An open portion 103 is formed in the insulation layer 102. The openportion 103 may include, for example, a first open portion 103A and asecond open portion 103B. The first open portion 103A exposes a part ofa surface of the substrate 101. The second open portion 103B is formedover the first open portion 103A. A width of the second open portion103B may be greater than a width of the first open portion 103A. Aconductive structure 104 is formed in the open portion 103. Theconductive structure 104 may include, for example, a first conductivepattern 105 and a second conductive pattern 107. The second conductivepattern 107 is formed over the first conductive pattern 105. A thirdconductive pattern 106 is formed between the first conductive pattern105 and the second conductive pattern 107. The third conductive pattern106 may be an ohmic contact layer. The first conductive pattern 105 isformed in the first open portion 103A. The second conductive pattern 107is formed in the second open portion 103B.

A first spacer 109 is formed over the sidewalls that define the firstopen portion 103A. A third spacer 111 is formed between the first spacer109 and the first conductive pattern 105. A second spacer 110 is formedover the third spacer 111 and the first spacer 109. The second spacer110 is formed over sidewalls that define the second open portion 103B tocap the air gap 108 and the first spacer 109. An insulation structure,including a first spacer 109 and the third spacer 111, is formed betweenthe first conductive pattern 105 and the sidewalis that define the firstopen portion 103A. The third spacer 111 is formed between the firstspacer 109 and the first conductive pattern 105. The second spacer 110is formed over the third spacer 111 and the first spacer 109. The secondspacer 110 is formed over sidewalls that define the second open region103B to cap the third spacer 111 and the first spacer 109.

The third spacer 111 may include, for example, a material having a lowdielectric constant. The third spacer 111 may include, for example, amaterial having a dielectric constant that is lower than a dielectricconstant of the first spacer 109 and a dielectric constant of the thirdspacer 111. The dielectric constant of the third spacer 111 has valuebetween a dielectric constant of air and a dielectric constant of SiO₂.For example, the third spacer 111 may include, for example, acarbon-containing material. The third spacer 111 may include, forexample, an amorphous carbon. The dielectric constant of the amorphouscarbon is lower than a dielectric constant of silicon oxide. Thedielectric constant of SiO₂ is 3.9 and dielectric constant of theamorphous carbon is equal to or less than about 3. The dielectricconstant of the amorphous carbon is controlled by a method for formingthe amorphous carbon or by an impurity content of the amorphous carbon.For example, the dielectric constant of amorphous carbon containinghydrogen is equal to or less than about 2.1.

In FIG. 3, since the third spacer 111 is formed of the carbon-containingmaterial having the low dielectric constant, a parasitic capacitancebetween two conductive patterns may be reduced between disposed adjacentto the first conductive pattern 105.

Since the second spacer 110 is formed over the sidewalis that define thesecond open portion 103B, a thickness of the second spacer 110 issufficient to cap the third spacer 111, so that the third spacer 111 isstably protected by the second spacer 110. Since a width of the secondopen region 103B is sufficient to form the second conductive pattern 107is secured even though the thickness of the second spacer 110 is thickerthan prior to. In addition, by enlarging an area to form the thirdconductive pattern 21, a contact resistance may be improved.

FIG. 4 is a cross sectional view illustrating an exemplary semiconductordevice.

Referring to FIG. 4, a plurality of conductive structures are formedover a substrate 201. The conductive structures include a firstconductive structure 202 and a second conductive structure 205. Aninsulation structure having an air gap 209 is formed between the firstconductive structure 202 and the second conductive structure 205. Afirst spacer 210 is formed over the first conductive structure 202. Theair gap 209 is formed between the first spacer 210 and the secondconductive structure 205. A second spacer 211 is formed over the air gap209 and the first spacer 210. Upper portions of the air gap 209 and thefirst spacer 210 are capped by the second spacer 211.

In detail, the substrate 201 may include, for example, a siliconsubstrate, a silicon germanium substrate, or the like. Furthermore, thesubstrate 101 may include, for example, a silicon-on-insulator (SOI)substrate.

The first conductive structure 202 may include, for example, a firstconductive pattern 203. The first conductive structure 202 may include,for example, a stack of the first conductive pattern 203 and aninsulation pattern 204. The first conductive pattern 203 may include,for example, a silicon-containing layer or a metal-containing layer. Thefirst conductive pattern 203 may include, for example, a stack asilicon-containing layer and a metal-containing layer. The firstconductive pattern 203 may include, for example, polysilicon, a metal, ametal nitride, a metal silicide, or the like. The first conductivepattern 203 may include, for example, a stack of a polysilicon layer anda metal layer. The first conductive pattern 203 may include, forexample, tungsten. The insulation pattern 204 may include, for example,an oxide, a nitride, or the like. The insulation pattern 204 mayinclude, for example, a hard mask pattern. The first conductivestructure 202 and the second conductive structure 205 are formed to be aline type or a pillar type. Further, one of the first conductivestructure 202 or the second conductive structure 205 may have line shapeextending in one direction. The other of the first conductive structure202 or the second conductive structure 205 may have a pillar shape.First conductive structures 202 may be regularly arranged on thesubstrate 201 at regular intervals. A width of the insulation pattern204 may be made smaller than a width of the first conductive pattern 203by a trimming process. A width of a lower portion of the insulationpattern 204, which contacts the first conductive pattern 203, issubstantially identical to a width of the first conductive pattern 203.One of the first conductive structure 202 and the second conductivestructure 205 may include, for example, a gate structure or a bit linestructure, and the other of the first conductive structure 202 or thesecond conductive structure 205 may include, for example, a contactplug. The contact plug may include, for example, a storage node contactplug, a landing plug, a metal contact plug, or the like.

The second conductive structure 205 may include, for example, the secondconductive pattern 206 formed between adjacent first conductivestructures 202. The second conductive structure 205 may include, forexample, a stack of a second conductive pattern 206 and a thirdconductive pattern 208. The second conductive pattern 206 may include,for example, a silicon-containing layer. The second conductive pattern206 may include, for example, a polysilicon layer. The second conductivepattern 206 has a height substantially the same as or greater than thatof the first conductive pattern 203. An open portion (not shown) isdefined between adjacent first conductive structures 202, and the secondconductive structure 205 is formed in the open portion. The open portionmay expose the first conductive structure 202.

The third conductive pattern 208 may include, for example, ametal-containing layer. The third conductive pattern 208 may include,for example, a metal, a metal silicide, a metal nitride, or the like.The third conductive pattern 208 may include, for example, a stack of abarrier layer and metal layer. The third conductive pattern 208 mayinclude, for example, a material comprising titanium or tungsten.

A fourth conductive pattern 207 is formed between the second conductivepattern 206 and the third conductive pattern 208. The fourth conductivepattern 207 may form an ohmic contact between the second conductivepattern 206 and the third conductive pattern 208. If the fourthconductive pattern 207 acts as the barrier layer, then an additionalbarrier layer would not be necessary.

The first spacer 210 is formed over the first conductive structure 202.An upper portion of the first spacer 210 is extended to a lower portionof the insulation pattern 204. A second spacer 211 is formed over anupper portion of the insulation pattern 204. A thickness of the secondspacer 211 is greater than a thickness of the first spacer 210. Thethickness of the second spacer 211 is sufficient to cap the air gap 209and the first spacer 210. The first spacer 210 and the second spacer 211include a material having a low dielectric constant. The low dielectricconstant material may include, for example, an oxide or a nitride. Thefirst spacer 210 and the second spacer 211 may include, for example, asilicon oxide, a silicon nitride, or a metal oxide. The first spacer 210may include, for example, a material having a high density. The secondspacer 211 may include, for example, a material having a low density.The first spacer 210 may include, for example, a silicon nitride. Thesecond spacer 211 may include, for example, a silicon oxide. The siliconoxide may include, for example, SiO₂. The silicon nitride may include,for example, SI₃N₄ or SiN. The second spacer 211 may include, forexample, a silicon oxide having a low density. The first spacer 210 actsas a passivation layer and the second spacer 211 acts as a cappingspacer.

The air gap 209 is formed by removing a sacrificial material that isformed between first spacer 210 and the second conductive pattern 206through a conversion process (as described above). After forming thesecond conductive pattern 206, the first spacer 210 and the secondspacer 211 are formed by removing the sacrificial material.

In FIG. 4, the air gap 209 is stably capped by the second spacer 211.Due to the air gap 209, a parasitic capacitance between the first andsecond conductive patterns 202 and 206 may be reduced.

Since the second spacer 211 is formed over the trimmed insulationpattern 204, a thickness of the second spacer 211 is sufficient to capthe air gap 209, so that the air gap 209 is stably protected by thesecond spacer 110. Even though, the thickness of the second spacer 211is thicker than prior to, a space sufficient to form the thirdconductive patterns 202 is secured. In addition, by enlarging an area toform the fourth conductive patterns 207, a contact resistance betweenthe second conductive pattern 206 and the third conductive pattern 208may be improved.

FIGS. 5A to 5I are cross sectional views illustrating an exemplarymethod for fabricating the semiconductor device of FIG. 4.

Referring to FIG. 5A, a plurality of first conductive structures 34 areformed over a substrate 31. The substrate 31 may include, for example, asemiconductor substrate. The substrate 31 may include, for example, asilicon substrate, a silicon germanium substrate, or the like.Furthermore, the substrate 31 may include, for example, asilicon-on-insulator (SOI) substrate.

The first conductive structures 34 are regularly arranged at a certaininterval. To form the first conductive structures 34, a hard maskpattern 33A is formed over a first conductive layer (not shown), and thefirst conductive layer is etched using the hard mask pattern 33A as anetch barrier to form a first conductive pattern 32. As a result, thefirst conductive structures 34 have a stack of the first conductivepattern 32 and the hard mask pattern 33A. The first conductive pattern32 may include, for example, a silicon-containing layer or ametal-containing layer. For example, the first conductive pattern 32 mayinclude, for example, polysilicon or tungsten. The first conductivepattern 32 may include, for example, a stack of a silicon-containinglayer and a metal-containing layer. For example, the first conductivepattern 32 may include, for example, a stack of a polysilicon layer anda tungsten layer. At this time, a barrier layer is formed between thepolysilicon layer and the tungsten layer. The first conductive pattern32 may include, for example, a stack conductive structure of apolysilicon layer, a titanium-containing layer, and a tungsten layer.The titanium-containing layer is used as a barrier layer, and mayinclude, for example, a stack of a titanium layer and a titanium nitridelayer. The hard mask pattern 33A may include, for example, an insulatingmaterial.

A first insulation layer 35A is formed over the first conductivestructures 34. The first insulation layer 35A may include, for example,a low-k material. The first insulation layer 35A may include, forexample, an oxide, a nitride, or the like. For example, the firstinsulating layer 35A may include a silicon nitride, a silicon oxide, orthe like. The first insulation layer 35A may be conformally formed overthe entire surface of the resulting structure comprising the firstconductive structures 34. The first insulation layer 35A will become aspacer in a subsequent process.

A second insulation layer 36A is formed over the first insulation layer35A. The second insulation layer 36A may include, for example, a siliconoxide. The second insulation layer 36A is formed over the firstinsulation layer 35A to fill spaces between the first conductivestructures 34. The second insulation layer 36A may include, for example,a material that can serve as an inter-layer insulation layer.

Referring to FIG. 5B, a planarization process is performed on the secondinsulation layer 36A to expose a surface of the first insulation layer35A.

The second insulation layer 36A is etched to form an open portion 37.After forming the open portion 37, the second insulation layer 36A isremoved. A mask pattern (not shown) may be used to form the open portion37. The open portion 37 is formed in a hole shape or a line shape. Theopen portion 13 is formed between the first conductive structures 34.The first insulation layer 35A is exposed at sidewalls defining the openportion 37.

The first insulation layer 35A may remain on the substrate 31 below theopen portion 37.

Referring to FIG. 5C, a sacrificial layer 38A is formed over the entiresurface of the resulting structure, including the open portion 37. Thesacrificial layer 38A may be conformally formed over the firstinsulation layer 35A. The sacrificial layer 38A may be etched during asubsequent process to form an air gap. The sacrificial layer 38A mayinclude, for example, a material having a low dielectric constant. Thesacrificial layer 38A may include, for example, a material for formingvolatile products by a conversion process (as described above). Thesacrificial layer 38A is formed at a temperature above at least 400° C.The dielectric constant of the sacrificial layer 38A has value between adielectric constant of air and a dielectric constant of SiO₂. Thesacrificial layer 38A may include, for example, a carbon-containingmaterial. The sacrificial layer 38A may include, for example, anamorphous carbon.

In an alternative implementation, after forming the open portion 37, thefirst insulation layer 35A and the sacrificial layer 38A may besequentially formed. Accordingly, the first insulation layer 35A and thesacrificial layer 38A may be formed to cover an exposed surface of thesubstrate 31, the sidewalls that define the open portion 37, and a topsurface of the hard mask pattern 33A.

Referring to FIG. 5D, a sacrificial pattern 38B is formed by selectivelyetching the sacrificial layer 38A. A dry etching process may be used toform the sacrificial pattern 38B. The dry etching process may include,for example, an etch-back process. Thus, the sacrificial pattern 38B isformed adjacent to the first conductive structures 34.

At this time, the first insulation layer 35A formed over the exposedsurface of the substrate 31 and the top surface of the hard mask pattern33A is selectively etched. A first spacer 356 may be formed byselectively etching the first insulation layer 35A. The first spacer 356may be formed over the first conductive structures 34. The sacrificialpattern 38B remains on the first insulation pattern 356. A dry etchingprocess may be used to form the first insulation pattern 35B. The dryetching process may include, for example, an etch-back process. Byforming the first insulation pattern 35B, a surface of the substrate isexposed. The sacrificial pattern 38B is separated from the substrate 31by a lower portion of the first insulation pattern 355.

As describe above, a dual spacer structure of the first spacer 356 andthe sacrificial pattern 38B is formed over the first conductivestructures 34. The dual spacer structure is formed over the sidewallsdefining the open portion 37. The open portion 37 may form to have aline type or a hole type.

Referring to FIG. 5E, a second conductive pattern 39 is formed to fill apart of the open portion 37. In other words, the second conductivepattern 39 is formed to be recessed in the open portion 37. The secondconductive pattern 39 may be formed by performing a planarizationprocess and a recessing process on a second conductive layer (notshown). The second conductive layer may be formed at a temperature belowabout 400° C. An etch-back process or a chemical mechanical polishing(CMP) process may be performed on the second conductive pattern 39. Thesecond conductive pattern 39 has a recessed surface lower than topsurfaces of the first conductive structures 34. The recessed surface ofthe second conductive pattern 39 is adjusted to have a height higherthan a top surface of the first conductive pattern 32. The height of therecessed surface of the second conductive pattern 39 may be adjusted tominimize a facing area to the first conductive pattern 32. Accordingly,parasitic capacitance between the first conductive pattern 32 and thesecond conductive pattern 39 may be reduced. The second conductivepattern 39 may include, for example, a silicon-containing layer. Thesecond conductive pattern 39 may include, for example, polysiliconlayer.

A part of the sacrificial pattern 38B is exposed after the secondconductive pattern 39 is recessed.

Referring to FIG. 5F, the sacrificial pattern 38B may be recessed toform a sacrificial spacer 38. The sacrificial pattern 38B may beselectively etched to form the sacrificial spacer 38. The part of thesacrificial pattern 38B that is exposed after the second conductivepattern 39 is recessed to a certain depth. An etch-back process may beapplied to recess the sacrificial pattern 38B.

A first spacer 35 may be formed by selectively etching the firstinsulation pattern 355. The sacrificial spacer 38 is formed byselectively etching the sacrificial pattern 38B.

An isotropic etching process may be used for recessing the first spacer35B and the sacrificial pattern 38B. The first spacer 35 and thesacrificial spacer 38 are formed between the second conductive pattern39 and the first conductive structures 34. In another exemplaryimplementation the second conductive pattern 39, the sacrificial spacer38 and the first spacer 35 may be simultaneously recessed.

Accordingly, the hard mask pattern 33A of first conductive structures 34are exposed by the forming process of the sacrificial spacer 38 and thefirst spacer 35.

Then, a trimming process is performed on the exposed hard mask pattern33A to form a trimmed hard mask pattern 33. The trimming process may beperformed by an isotropic etching process. The isotropic etching processfor forming the first spacer 35 and the trimming process for the hardmask pattern 33A may be the same process. That is, the isotropic etchingprocess for forming the first spacer 35 may performed by performing thetrimming process for the hard mask pattern 33A. In an exemplaryimplementation, an isotropic etching process for forming a sacrificialspacer 38 and an isotropic etching processes for forming the firstspacer 35B and the hard mask pattern 33A may be simultaneouslyperformed.

A width of sidewalls (33B) of the hard mask pattern 33A is decreased bythe trimming process and a width of a top portion of the open portion 37is increased by the trimming of the hard mask pattern 33A. A thicknessof a subsequent second spacer 40 will be increased by increasing thewidth of the top portion of the open portion 37. The sacrificial spacer38 will be entirely capped by the thick second spacer 40.

As describe above, the second open region 376 is formed by the trimmingprocess. The first open region 37A may contain, for example, the firstspacer 35 and the sacrificial spacer 38. The open region 37 may include,for example, the first open region 37A and the second open region 37B.The width of the second open region 37B may be greater than the width ofthe first open region 37A.

Referring to FIG. 5G, the second spacer 40 is formed. A third insulationlayer (not shown) is formed over the entire surface of the resultingstructure, including the trimmed hard mask pattern 33. The thirdinsulation layer may be conformally formed over the entire surface ofthe resulting structure, including the trimmed hard mask pattern. Anisotropic etching process may be used to form the second spacer 40. Theisotropic etching process may include, for example, an etch-backprocess. Accordingly, the second spacer 40 is formed over the trimmedhard mask pattern 33. That is, the second spacer 40 is formed over thetrimmed hard mask pattern 33 that define the second open region 37B. Thesecond spacer 40 may be formed by etching the third insulation layer.The second spacer 40 may include, for example, a material having a lowdielectric constant. The second spacer 40 may include, for example, amaterial having a low dielectric constant and a low density. The secondspacer 40 may include, for example, a porous dielectric material. Thesecond spacer 40 may include, for example, a silicon oxide, a siliconoxide having a low density, or the like. Volatile byproducts arediffused through the low density silicon oxide. The silicon oxide havinga low density is formed by a low temperature CVD. For example, thesilicon oxide having a low density may include, for example, SiO₂ formedby low temperature CVD. Since the second spacer 40 is formed at a lowtemperature below at least 400° C. the second spacer 40 has a lowdensity. The second spacer 40 may include a material having a lowdensity and being capable of diffusing by oxygen plasma in a plasmastripper.

The second spacer 40 has a sufficient thickness to cap an upper portionof the sacrificial spacer 38. The second spacer 40 is formed to exposethe upper portion of the first conductive pattern 32. That is, thesecond spacer 40 covers the first spacer 35 and the sacrificial spacer38. The upper surface of the second conductive pattern 39 is exposed.

Since the hard mask pattern 33A is trimmed, the second spacer 40 isformed to have an increased thickness. Also, an exposed area of thesecond conductive pattern 39 is wide, even though the thickness of thesecond spacer 40 is increased. The second spacer 40 is formed to cap theupper portions of the sacrificial spacer 38 and the first spacer 35, andto expose the upper portion of the first conductive pattern 32. That is,a thickness of the third insulation layer is determined to cap the upperportions of the sacrificial spacer 15. The width of the second openportion 13C is great, the thickness of the second spacer 17 is thick, sothat the sacrificial spacer 15 is entirely capped and the upper portionof the first conductive pattern 16 is widely exposed.

As describe above, each of the insulation structures formed sidewalls ofthe first conductive structures 34 is different from the insulationstructures formed sidewalls of the trimmed hard mask pattern 33 That is,a dual spacer structure including the first spacer 35 and thesacrificial spacer 38 is formed over the first conductive pattern 32 andlower sidewalk of the first conductive structures 34. A single spacerstructure comprising the second spacer 40 is formed over the trimmedhard mask pattern 33, and upper sidewalls of the first conductivestructures 34.

Referring to FIG. 5H, a conversion process 41 is performed to remove thesacrificial spacer 38. A material of the sacrificial spacer 38 isconverted to volatile byproducts 42 by the conversion process 41. Theconversion process 41 may include, for example, a decomposition process,a phase change process, or the like. The decomposition process and thephase change process turn a solid into a vapor or a gas. The volatilebyproducts 42 include vapor, gas, or the like. The volatile byproducts42 are easily removed by diffusing through the second spacer 40. Thesacrificial spacer 38 is removed without an etching process such as awet etching process.

If the sacrificial spacer 38 is, for example, an amorphous carbon, thenthe conversion process 41 may include, for example, an oxidationreaction process, such as an O₂ plasma treatment process. The O₂ plasmatreatment process may be performed using a plasma stripper. Theamorphous carbon is oxidized to form a vapor or a gas by the O₂ plasmatreatment process. For example, when the O₂ plasma permeates theamorphous carbon through the second spacer 40, the amorphous carbon isturned into volatile byproduct 42, such as carbon oxide CO2. Thevolatile byproducts 42 are diffuse through the second spacer 40. The lowdensity material of the second spacer 40 allows the O₂ plasma topermeate the second spacer 42 and allows the volatile byproducts 42 todiffuse out through the second spacer 42.

In contrast, the first spacer 35 blocks the diffusion of the volatilebyproducts 42, since the first spacer 35 may include, for example, ahigh density material. That is, the first spacer 35 acts as apassivation spacer for blocking the diffusion of the volatile byproducts42.

When the sacrificial spacer 38 is removed by the conversion process 41,a space previously occupied by the sacrificial spacer 38 becomes an airgap 43. Since the air gap 43 is capped by the second spacer 40, the airgap 43 is stably capped even though the sacrificial spacer 38 isremoved. A parasitic capacitance between adjacent second conductivepatterns 39 may be reduced by the air gap 43. Thus the air gap 43 andthe first spacer 35 are formed between the first conductive pattern 32and the second conductive pattern 39 and the air gap is formed betweenthe first spacer 35 and the second conductive pattern 39. If the secondconductive pattern 39 is a contact plug, then the air gap 43 may beformed to surround the second conductive pattern 39.

Referring to FIG. 5I, a third conductive pattern 44 is formed over asecond conductive pattern 39. The third conductive pattern 44 fills thesecond open portion 37B having the second spacer 40. The thirdconductive pattern 44 may include, for example, a metal-containinglayer. The third conductive pattern 44 may include, for example, atungsten layer. The third conductive pattern 44 may include, forexample, a stack of a barrier layer and a tungsten layer. The barrierlayer may include, for example, a stack of a titanium layer and atitanium nitride layer.

A fourth conductive pattern 45 is formed between the second conductivepattern 39 and the third conductive pattern 44. The fourth conductivepattern 45 may form an ohmic contact between the second conductivepattern 39 and the third conductive pattern 44. The fourth conductivepattern 45 may include, for example, a metal silicide. The fourthconductive pattern 45 may include, for example, a cobalt silicide. Toform the cobalt silicide, an annealing process is performed after acobalt layer is deposited over the second conductive pattern 39.Alternatively, the cobalt silicide may be directly deposited over thesecond conductive pattern 39. The deposited cobalt silicide may besimultaneously formed between the second conductive pattern 39 and thethird conductive pattern 44 and between the third conductive pattern 44and the second spacer 40.

When the third conductive pattern 44 is formed, a second conductivestructure 46, including the second conductive pattern 39, the fourthconductive pattern 45 and the third conductive pattern 44, is formed.The air gap 43 is formed between the second conductive pattern 39 andsidewalls that define the first open region 37A. The second spacersecond spacer 40 is formed between the third conductive pattern 44 andsidewalis that define the second open region 37B. The second spacer 40caps the air gap 43 and the first spacer 35.

The second conductive structure 46 may become a contact plug, anelectrode, or the like. Further, the second conductive structure 46 maybecome a bit line, a metal interconnection, a gate electrode, a wordline, or the like. For, example, if the first conductive structure 34 isa bit line, the second conductive structure 46 may be a storage contactplug.

In accordance with the exemplary implementations described above, byforming the air gap 43, a parasitic capacitance between the firstconductive structures 34 and the 36 may reduced.

Since the second spacer 40 is formed over the sidewalls that define thesecond open portion 37B, a thickness of the second spacer 40 is thickenough to cap the air gap 43, so that the air gap 43 is stably protectedby the second spacer 40. Even though, the thickness of the second spacer40 is thicker than prior to, a space sufficient to form the thirdconductive pattern 44 is secured. In addition, by enlarging an area toform the fourth conductive pattern 45, a contact resistance may beimproved.

The 212 may include, for example, a material having a low dielectricconstant. The third spacer 212 may include, for example, a materialhaving a low dielectric constant of lower dielectric constant than thefirst spacer 210 and the second spacer 211. Dielectric constant of thethird spacer 212 has a value between an airs to SiO₂. For example, thethird spacer 212 may include, for example, a carbon-containing material.The third spacer 212 may include, for example, an amorphous carbon.Dielectric constant of the amorphous carbon is lower than a siliconoxide. Dielectric constant of SiO₂ is 3.9 and dielectric constant of theamorphous carbon is equal to or less than 3. The dielectric constant ofthe amorphous carbon s controlled by a method for forming or impuritycontent. For example, the dielectric constant of the amorphous carboncontaining hydrogen is equal or less than 2.1.

The third spacer 212 corresponds to the sacrificial spacer 38 formedthrough the method for fabricating the semiconductor device show inFIGS. 5A to 5G. However, in this case, a conversion process is notperformed after the second spacer is formed. Since the conversionprocess is not performed, the sacrificial spacer 38 may remain. Thus,the remaining sacrificial spacer 38 is the third spacer 212.

In FIG. 6, since the third spacer 212 is formed of a carbon-containingmaterial having the low dielectric constant, a parasitic capacitancebetween two conductive patterns is reduced between disposed adjacent tothe second conductive pattern 206. The third spacer 212 is stablyprotected by the second spacer 211. Since the second spacer 211 isformed over the trimmed hard mask pattern 204, a thickness of the secondspacer 211 is thick enough to cap the third spacer 212, so that thethird spacer 212 is stably capped by the second spacer 211. Even though,the thickness of the second spacer 211 is thicker than prior to, a spacesufficient to form the third conductive patterns 208 is secured. Inaddition, by enlarging an area to form the fourth conductive patterns207, a contact resistance between the second conductive pattern 206 andthe third conductive patterns 208 may be improved.

FIGS. 7A to 7D illustrate a comparative example.

Referring to FIG. 7A, a plurality of first conductive structures 34 areformed over a substrate. Each of the first conductive structures 34 mayinclude, for example, a first conductive pattern 32 and a hard maskpattern 33A.

After forming an open portion (not shown) between the first conductivestructures 34, a first spacer 35B and a sacrificial spacer 38C areformed over the first conductive structures 34.

Subsequently, a recessed second conductive pattern 39 is formed.

Referring to FIG. 73, an air gap 43 is formed by removing the recessedsacrificial spacer 38C.

Referring to FIG. 7C, a capping spacer 40C is formed to cap the air gap45. Also, a second conductive structure 46 is formed by forming a fourthconductive pattern 45 and a third conductive pattern 44 over the secondconductive pattern 39 in a subsequent process.

In the comparative example, the sacrificial spacer 38C may be formed ofsilicon oxide, silicon nitride, titanium nitride, or the like. To formthe air gap 43, a wet etching process may be used to remove thesacrificial spacer 38C. Also, since the hard mask pattern 33A may not betrimmed, a thickness of the capping spacer 40C may be increased tostably cap the air gap 43. Accordingly, an exposed area of the secondconductive pattern 39 is reduced.

However, in the comparative example, a loss of surrounding structuresand a surface of the substrate 31 are incurred since the sacrificialspacer 38C is removed by the wet etching process.

In particular, if the thickness of the second spacer 40C decreases, thenthe air gap 43 is opened while the second spacer 40C is formed, as shownby reference numeral 43B in FIG. 7D. Due to the opened the air gap 43,the third conductive pattern 44 flows into the air gap 43, so it isdifficult to decreasing the parasitic capacitance by the air gap 43.Furthermore, if a thickness of the second spacer 40C increases, a spaceW to form the third conductive pattern 44 and a space to form the fourthconductive pattern 45 are decreased, thereby increasing a contactresistance between the third conductive patterns 44 and the fourthconductive patterns 45 may be increased

The etching process to removing the titanium nitride used as thesacrificial spacer 38C has a high level of difficulty. Therefore, it isdifficult to remove the titanium nitride using the wet etching process.Also, since an etch selectivity of the sacrificial spacer 38C is lowerthan the hard mask pattern 33A and the first spacer 35B, a loss of thehard mask pattern 33A and the first spacer 35B may be incurred.

Therefore, as can be seen by this comparative example, the air gap in anexemplary implementation may be formed without a loss of the surroundingstructures using the conversion process. In contrast, the etchingprocess of the comparative example results in a loss of surroundingstructures. Also, in the exemplary implementations, the sacrificialmaterial is essentially completely removed by the conversion process andthe air gap is stably capped by forming the air gap after forming thesecond spacer.

FIG. 8A illustrates exemplary memory cells of an exemplary semiconductordevice. FIG. 8B is a cross-sectional view of the memory cells takenalong line A-A′ of FIG. 8A. FIG. 8C is a cross-sectional view of thememory cells taken along line B-B′ of FIG. 8B.

For reference, the memory cells shown in FIG. 8A may include, forexample, DRAM memory cells.

Referring to FIGS. 8A to 8C, an active region 303 is defined by a deviceisolation region 302 in a substrate 301. A trench 320 is formed acrossthe active region 303. A gate dielectric layer 321 is formed along asurface of the trench 320. A buried gate electrode 322 is formed overthe gate dielectric layer 321 to partially fill the trench 320. Althoughnot illustrated, source/drain regions are formed in the substrate 301. Asealing layer 323 is formed over the buried gate electrode 322.

A bit line structure, comprising a bit line 307 extending in a directioncrossing the buried gate electrode 322, is formed. The bit linestructure may include, for example, the bit line 307, a bit line hardmask 308, and a bit line spacer 309. The bit line 307 is coupled to theactive region 303 via a bit line contact plug 306. The bit line contactplug 306 is formed in a bit line contact hole 305 that is formed in afirst inter-layer insulation layer 304. Sidewalls of the bit line hardmask 308 are trimmed, so that a width of the bit line hard mask 308 issmaller than a width of the bit line 307.

The storage node contact plug 311 is formed in the first and secondstorage node contact holes 310 and 317 that penetrate the firstinter-layer insulation layer 304 and a second inter-layer insulationlayer 319. The width of the second storage node contact hole 317 isincreased by the trimming the side ails of the bit line hard mask 308.The first storage node contact hole 310 may be enlarged in a horizontaldirection by an isotropic etching process. The storage node contact plug311 may include, for example, a first plug 312, an ohmic contact layer313, and a second plug 314. The first plug 312 may be a silicon plugincluding, for example, polysilicon. The second plug 314 may be a metalplug, including, for example, tungsten. The ohmic contact layer 313 mayinclude, for example, a metal silicide. The ohmic contact layer 313 mayinclude, for example, a cobalt silicide.

An insulating structure comprising an air gap 315 is formed between thestorage node contact plug 311 and the bit lime 307. That is, the firstplug 312 is formed away from the bit line 307 by the bit line spacer 309and the air gap 315. The air gap 315 is capped by a capping spacer 316.The air gap 315 and the capping spacer 316 is formed by the abovedescribed with respect to FIGS. 1-6. The capping spacer 316 maycorresponded to the second spacer 110, 211, 40 and the bit line spacer309 may corresponded to the first spacer 109, 210, 35. Accordingly, thecapping spacer 316 is formed over the trimmed sidewalls of the bit linehard mask 308.

A storage node 318 is formed over a storage node contact plug 311, andis connected to the active region 303 via the storage node contact plug311.

FIGS. 9A to 9K illustrate a modification to the exemplary memory cellsshown in FIGS. 8A-8C.

Referring to FIG. 9A, a substrate 51 may include, for example, silicon.The substrate 51 may include, for example, a silicon substrate, asilicon germanium substrate, or the like. Furthermore, the substrate 51may include, for example, a silicon-on-insulator (SOI) substrate.

A device isolation region 52 is formed in a substrate 301. The deviceisolation region 52 is formed by a shallow trench isolation (STI)process. An active region 53 is defined by the device isolation region52. The device isolation region 52 may formed by sequentially stacking awall oxide, a liner, and a fill material. The liner may include, forexample, a silicon nitride, a silicon oxide, or the like. The siliconnitride may include, for example, SI₃N₄, and the silicon oxide mayinclude, for example, SiO₂. The fill material may include, for example,a silicon oxide, such as spin-on dielectric (SOD). Furthermore, the fillmaterial may include, for example, a silicon nitride. In an alternativeimplementation, the liner may be entirely silicon nitride.

Although not illustrated, after forming the device isolation region 52,a buried gate electrode (reference numeral 322 shown in FIG. 8C) isformed. For example, after forming the trench by etching the activeregion 53 and the device isolation region 52, the buried gate electrode322 is formed in the trench. Then, the sealing layer 323 is formed overthe buried gate electrode 322. Before forming the buried gate electrode322, the gate dielectric layer is formed along a surface defining thetrench 320. The buried gate electrode 322 may formed by etching back ametal containing layer after the metal containing layer is formed tofill the trench 320. The metal-containing layer may include, forexample, a metal, such as titanium, tantalum, tungsten, or the like. Themetal-containing layer may include, for example, tantalum nitride (TaN),titanium nitride (TIN), tungsten nitride (WN), or tungsten (W). Forexample, the buried gate electrode 322 may have a single layer structureof TIN, TaN, or W, or a dual layer structure of TiN/W or TaN/W formed bystacking W over TiN or TaN. Furthermore, the buried gate electrode 323may have a dual layer structure of WN/W in which W is stacked over WN.In addition, the buried gate electrode 322 may include, for example, alow-resistance metal material. The sealing layer may serve to protectthe buried gate electrode 322 during a subsequent process. The sealinglayer may include, for example, an insulating material. The sealinglayer may include, for example, silicon nitride. After forming thesealing layer, source/drain regions is formed in the active region.

Referring back to FIG. 9A, a first interlayer insulation layer 54 isformed over the entire surface of the substrate 51. The first interlayerinsulation layer 54 may include, for example, a silicon nitride, asilicon oxide, or the like. An etch stop layer (not shown) comprisingsilicon nitride is formed over the first interlayer insulation layer 54.

The first interlayer insulation layer 54 is etched to form a bit linecontact hole 55 to expose a surface of a part of the substrate 51. Amask pattern (not shown) is used as an etch mask to form the bit linecontact hole 55. After forming the bit line contact hole 55, the activeregion 53 is recessed in a certain depth. Thus, a contact area betweenthe active region 53 and a bit line contact plug 56 formed in the bitline contact hole 55 may increase.

The bit line contact plug 56 is formed in the bit line contact hole 55.The bit line contact plug 56 is formed to fill the bit line contact hole55. After a conductive layer (not shown) is formed over the entiresurface of the resulting structure comprising the first interlayerinsulation layer 54, a planarization process is performed on theconductive layer, thereby forming the bit line contact plug 56. The bitline contact plug 56 may include, for example, a polysilicon layer or ametal layer.

A bit line 57 and a bit line hard mask 58A may be formed over the bitline contact plug 56. In an alternative implementation if the bit line57 and the bit line hard mask 58A are adjusted to have a width smallerthan a width of the bit line contact hole 55, then the bit line contactplug 56 is etched. In this case, although sidewalls defining the bitline contact hole 55 are exposed as the bit line contact plug 56 isetched, the exposed sidewalls are filled by using a bit line spacer 59.The bit line 57 may include, for example, a metal-containing layer, suchas tungsten. The bit line hard mask 58A may include, for example, asilicon nitride.

Although not illustrated, fabricating processes of the bit line contactplug 56, the bit line 57 and the bit line hard mask pattern 58A and thefabricating processes of gate structure of a transistor in a peripheralregion may be simultaneously performed.

A bit line spacer 59A is formed over the entire surface of the resultingstructure comprising the bit line hard mask pattern 58A. The bit linespacer 59A may be conformally formed. The bit line spacer 59A mayinclude, for example, a silicon nitride. The silicon nitride mayinclude, for example, a high density silicon nitride.

Referring to FIG. 9B, a second interlayer insulation layer 60 is formedover the bit line spacer 59A. The second inter-layer insulation layer 60is formed over the entire surface of the resulting structure comprisingthe bit line spacer 59A to fill spaces between the adjacent bit lines57. The second inter-layer insulation layer 60 is planarized to exposethe top surface of the bit line hard mask pattern 58A.

Referring to FIG. 9C, the second interlayer insulation layer 60 may beetched using a mask pattern (not shown) to form a storage node contacthole 61 is formed between the adjacent bit lines 57. The storage nodecontact hole 61 is self-aligned by the bit line spacer 59A formed overthe bit line 57. Thus, a passivation spacer 59 is formed over sidewallsdefining the storage node contact hole 61 that are exposed by thestorage node contact hole 61. The bit line spacer 59A remains below thestorage node contact hole 61.

A sacrificial layer 62A is formed over the entire surface of theresulting structure, including the storage node contact hole 61. Thesacrificial layer 62A is formed at a temperature above at east 400° C.The dielectric constant of the sacrificial layer 62A has value between adielectric constant of air and a dielectric constant of SiO₂. Thesacrificial layer 62A may include, for example, a carbon-containingmaterial. The sacrificial layer 62A may include, for example, anamorphous carbon.

Referring to FIG. 9D, the sacrificial spacer 626 may be formed over thesidewalls that define the storage node contact hole 61 by etch backprocess of the sacrificial layer 62A.

The bit line spacer 59A exposed by the (266) is etched to form a bitline spacer 59B. The bit line spacer 59B is formed over the bit line 57and the bit line hard mask pattern 58A. The bit line spacer 59B that isformed over the bit line hard mask pattern 58A is removed. Thesacrificial spacer 62B is formed over the bit line spacer 59B. Thesacrificial spacer 626 and the bit line spacer 59B form a dual spacerstructure.

The first inter-layer insulation layer 54 exposed by the bit line spacer59B is etched to enlarge the storage node contact hole 61 in a verticaldirection. Thus, a surface of the substrate 51 is exposed.

Referring to FIG. 9E, the first inter-layer insulation layer 54 isisotropically etched to enlarge a lower portion of the storage nodecontact holes 61 in a horizontal direction. When the first inter-layerinsulation layer 54 is isotropically etched, the sacrificial spacer 626and the bit line spacer 59B are used as a etch barrier layer. When thefirst inter-layer insulation layer 54 is isotropically etched, a part ofthe device isolation region 52 is etched.

Referring to FIG. 9F, a first plug 63 is formed in the storage nodecontact hole 61. A conductive layer (not shown) is formed over theentire surface of the resulting structure to fill the storage nodecontact hole 61. The first plug 63 is formed by recessing the conductivelayer. The first plug 63 may have a surface that is higher than a topsurface of the bit line 57. The height of the surface of the first plug63 is adjusted to minimize a facing area to the bit line 57.Accordingly, parasitic capacitance between the first plug 63 and the bitline 57 may be reduced. The first plug 63 may include, for example, asilicon or a metal. The first plug 63 may include, for example,polysilicon. The first plug 63 is formed at a temperature below at least400° C. The top portion of the sacrificial spacer 62B is exposed afterthe first plug 63 is formed.

Referring to FIG. 9G, portions of the sacrificial spacer 62B and the bitline spacer 59B that extend above the first plug 63 may be removed by anisotropic etching process. The sacrificial spacer 62 is formed by theisotropic etching process of the sacrificial spacer 62BA top portion ofthe bit line spacer 59B, which is exposed by the removal of thesacrificial spacer 62, is selectively etched by an isotropic etchingprocess to form a passivation spacer 59.

By using an isotropic etching process, a recessed plug structureincluding the sacrificial spacer 62, which surrounds the first plug 63,is formed. Upper surfaces of the passivation spacer 59 and thesacrificial spacer 62 are aligned to be substantially co-planar with anupper surface of the first plug 63.

Then, a trimming process is performed on the bit line hard mask pattern58A. The trimming process may be performed by an isotropic etchingprocess. The same isotropic etching process may be used to etch the bitline spacer 59B and trim the bit line hard mask pattern 58B.

The trimming process decreases a width of the bit line hard mask pattern58 and increases a width of an upper portion of the storage node contacthole 61.

Similar to the second storage node contact hole 317 (as shown in FIGS.8A and 8C) a second storage node contact hole 64 is formed by thetrimming process of the bit line hard mask pattern 58. The storage nodecontact hole having the first plug 63 and the sacrificial spacer 62 is afirst storage node contact hole 65. A width of the second storage nodecontact hole 64 may be greater than a width of the first storage nodecontact hole 65.

Referring to FIG. 9H, a capping spacer 66 is formed. A second insulationlayer not shown) is conformally formed over the entire surface of theresulting structure, including the bit line hard mask pattern 58. Then,the second insulation layer may be etched to form the capping spacer 66.The capping spacer 66 may be formed by a dry etching process. Forexample, the dry etching process may include, for example, an etch backprocess. The capping spacer 66 is formed over the bit line hard maskpattern 58. The capping spacer 66 may include, for example, a materialhaving a low dielectric constant. The capping spacer 66 may include, forexample, a low density silicon oxide. The low density silicon oxide maybe formed by a low temperature CVD. The capping spacer 66 may include,for example, a porous dielectric material. Since the capping spacer 66is formed at a low temperature below at least 400° C., the secondinsulation layer has a low density. The capping spacer 66 may include,for example, a material having a low density and being capable ofdiffusing oxygen plasma from a plasma stripper.

The capping spacer 66 is formed over a third conductive pattern 44. Thecapping spacer 66 is formed to cap the upper portion of the sacrificialspacer 62 and to expose the upper portion of the first plug 63. That is,the capping spacer 66 is formed to cover the passivation spacer 59 andthe sacrificial spacer 62 and to expose the upper portion of the firstplug 63.

As described above, an air gap 69 is formed by removing the sacrificialspacer 62 by the conversion process 67. Since the air gap 69 is cappedby the capping spacer 66, the air gap 69 is stably capped even thoughthe sacrificial spacer 62 is removed. By forming the air gap 69, aparasitic capacitance between adjacent first plugs 63 may be decreased.The air gap 69 is formed to surround the first plug 63.

Referring to FIG. 9J, a second plug 71 is formed over the first plug 63.The second plug 71 fills the second storage node contact hole 64. Thesecond plug 71 may include, for example, a metal-containing layer. Thesecond plug 71 may include, for example, a tungsten layer. The secondplug 71 may include, for example, a stack of a titanium layer, atitanium nitride layer, and a tungsten layer. An ohmic contact: layer 70is formed between the first plug 63 and the second plug 71. The ohmiccontact layer 70 may include, for example, a metal silicide. The ohmiccontact layer 70 may include, for example, a cobalt silicide. To formthe cobalt silicide, an annealing process may be performed after acobalt layer is deposited over the first plug 63. Alternatively, cobaltsilicide may be directly deposited over the first plug 63. The cobaltsilicide may be simultaneously deposited between the first plug 63 andthe second plug 71 and between the second plug 71 and the capping spacer66. If the first plug 63 includes, for example, a silicon-containinglayer, then and the second plug 71 may include, for example, ametal-containing layer. The first plug 63 and the second plug 71 arecomposed of a semi-metal plug structure.

As described above, when the second plug 71 is formed, the storage nodecontact plug 72 comprising the first plug 63, the ohmic contact layer 70and the storage node contact plug 72. Accordingly, the air gap 69 isformed between the storage node contact plug 72 and the bit line 57. Theair gap is capped by the capping spacer 66.

Referring to FIG. 9K, a storage node 73 is formed the storage nodecontact plug 72. Though not illustrated, a dielectric layer and a platenode is further formed over the storage node 73.

The exemplary semiconductor device may be applied to DRAM (DynamicRandom Access Memory). Without being limited thereto, however, thesemiconductor device is applied to SRAM (Static Random Access Memory),flash memory, FeRAM (Ferroelectric Random Access Memory), MRAM (MagneticRandom Access Memory), PRAM (Phase Change Random Access Memory), or thelike.

FIG. 10 is a schematic diagram of an exemplary memory card.

Referring to FIG. 10, the memory card 400 may include, for example, acontroller 410 and a memory 420. The controller 410 and the memory 420may exchange electrical signals. For example, the memory 420 and thecontroller 410 may exchange data according to a command of thecontroller 410. Accordingly, the memory card 400 may store data in thememory 420, or output data to the outside from the memory 420. Thememory 420 may include, for example, the above-described air gap or theabove-described carbon-containing spacer. The memory card 400 may beused, for example, as a data storage media of various portable devices.For example, the memory card 400 may include, for example, a memorystick card, a smart media card (SM), a secure digital card (SD), a minisecure digital card (min SD), or a multi-media card MMC).

FIG. 11 is a block diagram illustrating an exemplary electronic system.

Referring to FIG. 14, the electronic system 500 may include, forexample, a processor 510, an input/output device 530, and a chip 520,which perform data communication through a bus 540. The processor 510serves to perform a program operation and control the electronic system500. The input/output device 530 may be used to input or output data ofthe electronic system 500. The electronic system 500 may be connected toan external device, for example, a personal computer or network, andexchange data with the external device through the input/output device530. The chip 520 may store codes and data for the operation of theprocessor 510, and may process a part of operations assigned by theprocessor 510. For example, the chip 520 may include, for example, theabove-described air gap or carbon-containing spacer. The electronicsystem 500 may include various electronic control devices requiring thechip 520. For example, the electronic system 500 is used in a mobilephone, an MP3 player, a navigation system, a solid state disk (SSD), ora household appliance.

Although various exemplary implementations of the have been describedfor illustrative purposes, it will be apparent to those skilled in theart that various changes and modifications is made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

What is claimed is:
 1. A method for fabricating a semiconductor device,the method comprising: forming, over a substrate, a plurality of bitline structures, each including a stacked bit line and a hard maskpattern; forming an inter-layer insulation layer over the plurality ofbit line structures; forming, by etching the inter-layer insulationlayer, a contact hole between the plurality of bit line structures;forming a carbon-containing spacer on sidewalls, of the plurality of bitline structures, that define the contact hole; forming a first plug inthe contact hole to form a recess plug structure, including thecarbon-containing spacer, wherein the carbon-containing spacer islocated between the first plug and the sidewalls of the contact hole;removing the carbon-containing spacer to expose sidewalls of the hardmask pattern; reducing a thickness of the exposed sidewalls of the hardmask pattern; forming a capping spacer to cap the carbon-containingspacer and the reduced thickness sidewalls of the hard mask pattern; andforming an air gap between the bit line and the first plug by convertingthe carbon-containing spacer to a volatile form.
 2. The method of claim1, further comprising: forming a bit line spacer over the plurality ofbit line structures; and wherein the forming the carbon-containingspacer on the sidewalls of the bit line structures that define thecontact hole further comprises: forming the carbon-containing spacerover the bit line spacer.
 3. The method of claim 2, wherein the bit linespacer includes an insulation material having a density that issufficiently high as to prevent the converted carbon-containing spacerfrom diffusing through the bit line spacer.
 4. The method of claim 1,wherein the carbon-containing spacer includes amorphous carbon.
 5. Themethod of claim 1, wherein the converting the carbon-containing spacerto a volatile form comprises: volatilizing the carbon-containing spacervia an oxygen plasma treatment.
 6. The method of claim 1, wherein thecapping spacer includes an insulation material having a density that issufficiently low as to allow the converted carbon-containing spacer todiffuse through the capping spacer.